This invention relates to image forming apparatuses such as copiers and printers in which a plurality of sheet transport routes are provided to transport a sheet toward a destination of a plurality of destinations different from each other and the respective transport routes are exposed outside of a main body of the apparatus by opening a cover individually provided in correspondence to the transport routes.
A construction of an image forming apparatus as shown in FIG. 5 is known in which a sheet after an image transfer is transported along a certain transport route of a plurality of transport routes and discharged outside a main body of the apparatus.
FIG. 5 is a partially enlarged diagram of the construction. In FIG. 5, 302 is an imaging unit of the apparatus. The imaging unit 302 includes a photoreceptor 300 and a transfer roller 301. An image transfer is performed by the imaging unit 302.
Specifically, an electrostatic latent image is formed on an outer circumference of the photoreceptor 300 based on an image read from a document. By electrically attracting charged toner onto the latent image, the latent image is developed into a toner image on the surface of the photoreceptor 300. The toner image on the photoreceptor surface is electrically attracted to a copy sheet transported to the photoreceptor 300 due to a transfer voltage applied between the photoreceptor 300 and the transfer roller 301 to transfer the toner image onto the copy sheet. In this way, the toner image is transferred onto the sheet.
Fixing rollers 303, 303 are arranged downstream of the imaging unit 302 with respect to the sheet transport direction (indicated by the upward-directing arrow in FIG. 5). After passing the imaging unit 302, the sheet has the toner image fixed thereon by the fixing rollers 303, 303 while being applied with a heat.
A transport route formed downstream of the fixing rollers 303, 303 is branched into a transport route 305 communicating with a discharge port 307 and a transport route 304 communicating with a discharge port 308 opposite to the discharge port 307. A sheet after an image fixation is selectively transported either along the transport route 304 or the transport route 305 by a route changer mechanism.
Specifically, switching members 306, 306 as the route changer mechanism are provided at the junction of the transport routes 304, 305. The switching members 306, 306 are pivotable about respective axes of pivots to selectively guide a sheet after an image fixation to the transport route 304 and the transport route 305. When the switching members 306, 306 are set in a state shown by the solid line in FIG. 5, the sheet is transported toward the transport route 305 while guided along the track indicated by the bold solid line P in FIG. 5 and discharged onto a discharge tray 313 via the discharge port 307. In this case, the sheet is discharged onto the discharge tray 313 with the side carrying an image facing downward.
On the other hand, when the switching members 306, 306 are set in a state shown by the dashed line in FIG. 5, the sheet is transported toward the transport route 304 and discharged onto a finisher (not shown) or a discharge tray (not shown) with the side carrying an image facing upward.
Also, when the switching members 306, 306 are set in the dashed-line state in FIG. 5 to guide a sheet along the transport route 304, the transport routes 304, 305 are communicated to each other. Accordingly, in this state, the transport routes 304, 305 function as a switchback route to guide a sheet toward the discharge port 308 along the track indicated by the broken line P' in FIG. 5 by performing the following operations.
Specifically, first, the switching members 306, 306 are set in the solid-line state to temporarily transport a sheet toward the discharge port 307. When a tail end of the sheet in the transport direction reaches a certain position between a discharge roller pair 309, 309 provided near the discharge port 307 and the switching member 306, the discharge roller 309 is driven in a reverse direction. At this time, changing the posture of the switching members 306, 306 to the dashed-line state allows the sheet to be transported toward the discharge port 304 along the transport routes 305, 304.
More specifically, in the above state when the switchback route is provided by the transport routes 304, 305, connecting the transport route 304 to an access route (not shown) via the discharge port 308 and connecting the access route to the imaging unit 302 enables a double sided image transfer by feeding the sheet after a first image transfer again to the imaging unit 302 while utilizing the switchback route and the access route. The access route connecting the transport route 304 and the imaging unit 302 may be provided by mounting an external device on a side wall of the apparatus main body, e.g., a side wall of the apparatus on the same side as a cover 310 in which the discharge port 308 is formed.
The cover 310 is openably mounted on the side wall of the apparatus, and opening the cover 310 renders the transport route 304 accessible to outside of a main body of the apparatus. Likewise, a cover 311 is openably mounted on a top portion of the apparatus near the discharge port 307. Opening the cover 311 renders the transport route 305 accessible to outside of the main body of the apparatus. Opening the cover 310 (311) enables removing a jammed sheet in the transport route 304 (305) and maintenance service of the transport route 304 (305).
In the above apparatus, in the case where a sheet is jammed inside the apparatus main body near the switching member 306, an operator has a difficulty in judging which cover should be opened to remove the jammed sheet. Accordingly, what happened for most cases is that the operator at randomly opens the cover 310 (or 311) trying to confirm the position of the jammed sheet. When the operator judges it easier, after the trial opening, to remove the jammed sheet by opening the other cover 311 (or 310), he/she has to open the other cover 311 (or 310) in addition to the opening of the cover 310 (or 311). This operation is time-consuming and cumbersome.
Also, it is sometimes the case that merely opening one of the covers 310, 311 does not allow the operator to properly judge the position of the jammed sheet, thereby deterring the removal of the jammed sheet.
In view thereof, there is a demand for an image forming apparatus with an improved serviceability such as quick removal of jammed sheet and easy maintenance service.